The present invention relates to novel methods of forming a conductive pattern.
Photolithography is conventionally utilized for forming conductive patterns on, for example, plastic substrates or inorganic substrates, in production processes of wiring boards, display panels, etc.
A known method of forming a conductive pattern comprises, for example, the steps of: applying to a substrate surface a conductive pigment paste prepared by dispersing a conductive pigment such as silver powder in a photosensitive resin, to form a photosensitive conductive layer; irradiating the surface of the conductive layer with an electron beam or ultraviolet light through a photomask; developing the conductive layer; and optionally baking the conductive layer.
The above method, however, has the following problems: the conductive layer is incapable of forming a sharp pattern owing to its insufficient photosensitivity; the photosensitive resin is used in a large quantity and thus generates a great amount of gas when baked, thereby causing environmental problems; and the application of the method is limited because of difficulties in obtaining a thick conductive layer.
An object of the present invention is to provide a novel method of forming a conductive pattern free from the problems of the prior art.
Another object of the present invention is to provide a novel method of forming a conductive pattern, which is capable of forming a sharp pattern, free from environmental problems, and applicable for a wide variety of purposes.
Other objects and features of the present invention will become apparent from the following description.
The present invention provides a method of forming a conductive pattern, comprising the steps of:
(1) depositing a conductive coating-forming resin layer and an energy beam-sensitive coating layer on a substrate in this order;
(2) irradiating a surface of the energy beam-sensitive coating layer with an active energy beam or heat rays directly or through a mask so as to obtain a desired pattern;
(3) developing the energy beam-sensitive coating layer to form a resist pattern coating from the energy beam-sensitive coating layer; and
(4) removing revealed portions of the conductive coating-forming resin layer by development.
The present invention also provides a method of forming a conductive pattern, comprising the steps of:
(1) depositing a conductive coating-forming resin layer and an energy beam-sensitive coating layer on a substrate in this order;
(2) irradiating a surface of the energy beam-sensitive coating layer with an active energy beam or heat rays directly or through a mask so as to obtain a desired pattern; and
(3xe2x80x2) developing the energy beam-sensitive coating layer and the conductive coating-forming resin layer simultaneously.
The present inventors carried out extensive research to solve the problems of the prior art, and found that the problems can be solved when an energy beam-sensitive coating layer is deposited over the surface of a conductive coating-forming resin layer on a substrate, and the surface of the energy beam-sensitive coating layer is irradiated with an active energy beam or heat rays directly or through a mask for forming a desired relief pattern, followed by sequential or simultaneous development of the energy beam-sensitive coating layer and the conductive coating-forming resin layer. The present invention has been accomplished based on these findings.
Each step of the method of the present invention will be described below in detail.
Step (1)
In the step (1), a conductive coating-forming resin layer and an energy beam-sensitive coating layer are deposited on a substrate in this order.
The substrate may be, for example, an electrically insulating glass plate, a glass-epoxy plate or any of various plastic substrates. Examples of plastic substrates include films and plates of polyethylene terephthalate, polyimide or the like. The conductive coating-forming resin as such can be used as a plastic substrate. Further, the substrate may have a circuit pattern previously formed thereon.
The conductive coating-forming resin layer is an uncured resin layer which will be finally formed into a conductive pattern. The resin layer may be one substantially non-curable with the energy of heat rays or light beam radiated onto the surface of the energy beam-sensitive coating layer, or may be one curable by post-treatment with heat or light.
The resin for use in the conductive coating-forming resin layer may be conductive or non-conductive. When a conductive resin is used as a resin component for a conductive coating layer, the conductive resin layer may be formed from the conductive resin itself. However, the conductive resin may be used in combination with not only a conductive transparent pigment, a conductive color pigment or like conductive material, but also a non-conductive or semi-conductive, transparent or color pigment. On the other hand, when a non-conductive resin is used, the resin is rendered conductive by adding a conductive transparent pigment, a conductive color pigment or like conductive material. The non-conductive resin can be evaporated by, for example, post-heating, to obtain a conductive coating layer made of the remaining conductive pigment or like conductive material.
It is preferred that the coating formed from the conductive coating-forming resin layer has a volume resistivity not greater than 109 xcexa9.cm, in particular 1 xcexa9.cm to 108 xcexa9.cm.
The conductive coating-forming resin layer preferably has a glass transition temperature higher than the temperature to be employed for development of the resin layer. Stated specifically, in the case where the resin layer is developed using a treating solution, the resin layer has a glass transition temperature that is preferably higher, more preferably at least about 5xc2x0 C. higher, further more preferably about 10xc2x0 C. to 200xc2x0 C. higher, than the temperature of the treating solution. In the case where the resin layer is developed using a powder such as sandblast, the resin layer has a glass transition temperature that is preferably higher, more preferably at least about 5xc2x0 C. higher, further more preferably about 10xc2x0 C. to 200xc2x0 C. higher, than the temperature of the treating atmosphere. If the glass transition temperature is lower than the temperature for development, a high-resolution pattern is difficult to obtain. The glass transition temperature can be determined by DSC (differential scanning calorimetry).
The resin composition constituting the conductive coating-forming resin layer is not limited and may be varied according to the substrate for use in the method of the invention or the product to be obtained by the method. For example, a resin composition is usable which comprises a heat-curable or thermoplastic resin, a photocurable resin or like resin component, and optional component(s) such as a conductive transparent pigment, a conductive color pigment or like conductive material, or a non-conductive transparent pigment, a non-conductive color pigment or like non-conductive material.
Resins usable for forming the conductive coating-forming resin layer include, for example, acrylic resins, polyester resins, alkyd resins, organic silicon resins, epoxy resins, melamine resins, vinyl resins, phenol resins, fluororesins, polyurethane resins, oil-soluble polyimide-modified resins, inorganic silicon resins, and modified resins of at least two of these resins.
When using these resins having the above specified glass transition temperature, the conductive coating-forming resin layer can be removed without reduction of resolution, in the case where the resin layer is subjected to powder treatment such as development by blasting, after pattern formation. In the case where the resin layer is treated with a developer after pattern formation, it is preferable to use, as a conductive coating-forming resin, a resin which has the above specified glass transition temperature and is soluble or dispersible in an acid, an alkali, water or an organic solvent in order to facilitate the treatment with a developer. The conductive coating-forming resin is developable with an alkaline developer when it contains acid group(s); developable with an acid developer when it contains basic group(s); developable with a water developer when it is water-soluble; and developable with an organic solvent developer when it is soluble or dispersible in an organic solvent.
A typical example of acid groups which may be contained in the conductive coating-forming resin is carboxyl. A preferable carboxyl content is such that the resin has an acid value of about 10 to 700 mg KOH/g, in particular about 20 to 600 mg KOH/g. If the resin has an acid value less than about 10 mg KOH/g, the conductive coating-forming resin layer will not be sufficiently removed with an alkaline developer, thus failing to form a high resolution pattern. On the other hand, if the resin has an acid value more than about 700 mg KOH/g, the conductive coating-forming resin layer is excessively removed with an alkaline developer, thus failing to form a high resolution pattern. Therefore, an acid value outside the specified range is undesirable. A typical example of basic groups is amino groups. A preferable amino group content is such that the resin has an amine value of about 20 to 650, in particular about 30 to 600. If the resin has an amine value less than about 20, the conductive coating-forming resin layer will not be sufficiently removed, thus failing to form a high resolution pattern. On the other hand, if the resin has an amine value more than about 650, the conductive coating-forming resin layer is excessively removed, thus failing to form a high resolution pattern. Therefore, an amine value outside the specified range is undesirable.
Examples of acid group-containing resins include acid group-containing acrylic resins, acid group-containing polyester resins, acid group-containing alkyd resins, acid group-containing organic silicon resins, acid group-containing vinyl resins, acid group-containing phenol resins, acid group-containing fluororesins, acid group-containing polyurethane resins, and modified resins of at least two of these resins.
Examples of basic group-containing resins include basic group-containing acrylic resins, basic group-containing polyester resins, basic group-containing alkyd resins, basic group-containing organic silicon resins, basic group-containing vinyl resins, basic group-containing phenol resins, basic group-containing fluororesins, basic group-containing polyurethane resins, alkali silicate resins, and modified resins of at least two of these resins.
Examples of water-soluble resins include polycarboxylic acid resins, cellulose resins, polyvinyl alcohols, melamine resins and onium salt group-containing resins.
Examples of organic solvent-soluble resins include acrylic resins, polyester resins, alkyd resins, organic silicon resins, epoxy resins, vinyl resins, phenol resins, melamine resins, fluororesins, polyurethane resins, oil-soluble polyimide-modified resins, inorganic silicon resins, and modified resins of at least two of these resins. These resins may contain acid or basic group(s).
Usable heat-curable resins for forming a conductive coating include, for example, self-curing resins or combinations of a curable functional group-containing resin and a curing agent. Examples of self-curing resins include melamine resins, and silicon resins containing hydrolyzable group(s) (such as alkoxysilyl or hydroxysilyl). Examples of combinations of a curable functional group-containing resin and a curing agent include: epoxy resin/phenol resin; hydroxyl-containing resin/polyisocyanate; hydroxyl-containing resin/amino resin; epoxy resin/carboxylic acid or carboxylic anhydride; and epoxy resin/polyamine.
The conductive coating-forming resin may be a photocurable conductive coating-forming resin. Examples of such resins include photocurable resins mentioned hereinafter for use in the energy beam-sensitive coating layer.
The conductive coating-forming resin layer may contain a resin for development to impart to the resin layer, a glass transition temperature that is, for example, at least 5xc2x0 C. higher than the temperature for development of the resin layer. Usable as the resin for development is a resin which is capable of rendering the resin layer developable with the developer (such as dissolution inhibitor). The resin for development may be employed as the main component or an additive resin of the conductive coating-forming resin. The resin for development may remain in the coating formed in the final step.
Examples of conductive pigments and like conductive materials that may be added to the conductive coating-forming resin include known conductive materials such as silver, copper, iron, manganese, nickel, aluminum, cobalt, chromium, lead, zinc, bismuth, ITO (indium-tin oxide) and like metals; alloys comprising at least one of these metals; oxides of these metals; and materials comprising these conductive materials coated or deposited on the surface of insulating materials. Further, non-metallic conductive materials, such as conductive polymers, can be used.
Also usable as a conductive material is a tin dioxide powder doped with antimony, in which a semi-conductive tin dioxide component is doped with an antimony component to form a donor level of electrons and increase the conductivity. The antimony-doped tin dioxide powder can be used singly, or as a coating on another material. The material may be, for example, titanium oxide, potassium titanate, aluminum borate, barium sulfate, mica, silica or the like.
The conductive coating-forming resin layer may contain, where necessary, a heat-fusible inorganic powder (such as a glass frit), a coloring agent (such as a pigment or a dye), a filler or other additives.
The conductive coating-forming resin layer can be formed on the substrate by a process suitable for the purpose without limitation. Typical examples include: a process comprising dissolving or dispersing any of the above conductive coating-forming resins in a suitable solvent such as an organic solvent or water, applying the resulting solution or dispersion of the conductive coating-forming resin to a substrate by coating or printing, and evaporating the solvent; a process comprising heat-molding pellets of the conductive coating-forming resin into a suitable shape; and a process comprising applying a powder of the conductive coating-forming resin to a suitable portion and melting the powder by heating. The conductive coating-forming resin layer may be deposited on a substrate, or the resin layer as such can be used as a substrate. The thickness of the resin layer may be varied according to the intended use, and is preferably about 1 to 100 xcexcm, in particular about 2 to 80 xcexcm when the resin layer is formed on a black matrix or like material by coating or printing. When the resin layer is used as a substrate formed by molding or like means, it has a thickness of preferably about 100 xcexcm to 10 mm, in particular about 200 xcexcm to 5 mm.
Subsequently, an energy beam-sensitive coating layer is deposited on the surface of the conductive coating-forming resin layer formed on a substrate.
Known energy beam-sensitive coating layers can be used in the invention without limitation, as long as they are capable of changing in developer solubility when cured or decomposed by irradiation with an active energy beam or heat rays, and thereby forming a resist pattern coating.
Resin compositions usable for forming the energy beam-sensitive coating layer include, for example, organic solvent-based positive photosensitive resin compositions, organic solvent-based negative photosensitive resin compositions, aqueous positive photosensitive resin compositions, aqueous negative photosensitive resin compositions and like liquid photosensitive resist resin compositions; positive photosensitive dry films, negative photosensitive dry films and like photosensitive dry films; organic solvent-based negative heat-sensitive resin compositions, aqueous negative heat-sensitive resin compositions and like liquid heat-sensitive resin compositions; and negative heat-sensitive dry films and like heat-sensitive dry films.
In particular, a negative or positive resin composition sensitive to visible light is preferred as the composition for forming the energy beam-sensitive coating layer.
Examples of negative photosensitive resin compositions include conventional resin compositions containing a photocurable resin, a photoinitiator and where necessary, a photosensitizer.
The photocurable resin is not limited, and may be a conventionally used photocurable resin which has photosensitive group(s) crosslinkable by light irradiation, and which contains ionic group(s) (anionic or cationic group(s)) so that unexposed portions of the coating layer can be removed by dissolution in an alkaline or acid developer.
The photocurable resin contains unsaturated group(s) such as acryloyl, methacryloyl, vinyl, styryl or allyl.
Of ionic groups, a typical example of anionic groups is carboxyl. A preferred carboxyl content is such that the resin has an acid value of about 10 to 700 mg KOH/g, in particular about 20 to 600 mg KOH/g. If the acid value is less than about 10 mg KOH/g, uncured portions will not be removed sufficiently, resulting in a pattern with unsatisfactory resolution. On the other hand, if the acid value is more than about 700 mg KOH/g, cured portions will be likely to be removed, resulting in a pattern with unsatisfactory resolution. Thus, an acid value outside the specified range is undesirable. A typical example of cationic groups is amino groups. A preferred amino group content is such that the resin has an amine value of about 20 to 650, in particular about 30 to 600. If the amine value is less than about 20, uncured portions will not be removed sufficiently, resulting in a pattern with unsatisfactory resolution. On the other hand, if the amine value is more than about 650, cured portions Will be likely to be removed, resulting in a pattern with unsatisfactory resolution. Thus, an amine value outside the specified range is undesirable.
Examples of anionic resins include resins prepared by reacting a polycarboxylic acid resin with, for example, glycidyl(meth)acrylate or like monomer to introduce unsaturated group(s) and carboxyl group(s) into the resin.
Examples of cationic resins include resins prepared by addition reaction of a hydroxyl- and tertiary amino group-containing resin with a reaction product of a hydroxyl-containing unsaturated compound and a diisocyanate compound.
As the anionic or cationic resin, any of the photocurable resins shown in Japanese Unexamined Patent Publication No. 1991-223759 are usable.
Examples of photoinitiators include benzophenone, benzoin methyl ether, benzoin isopropyl ether, benzyl xanthone, thioxanthone, anthraquinone and like aromatic carbonyl compounds; acetophenone, propiophenone, xcex1-hydroxyisobutylphenone, xcex1,xcex1xe2x80x2-dichloro-4-phenoxyacetophenone, 1-hydroxy-1-cyclohexylacetophenone, diacetylacetophenone, acetophenone and like acetophenones; benzoyl peroxide, t-butylperoxy-2-ethylhexanoate, t-butylhydroperoxide, di-t-butyldiperoxyisophthalate, 3,3xe2x80x2,4,4xe2x80x2-tetra(t-butylperoxycarbonyl)benzophenone and like organic peroxides; diphenyl iodobromide, diphenyliodonium chloride and like diphenyl halonium salts; carbon tetrabromide, chloroform, iodoform and like organic halides; 3-phenyl-5-isooxazolone, 2,4,6-tris(trichloromethyl)-1,3,5-triazine benzanthrone and like heterocyclic or polycyclic compounds; 2,2xe2x80x2-azo(2,4-dimethylvaleronitrile), 2,2-azobisisobutyronitrile, 1,1xe2x80x2-azobis(cyclohexane-1-carbonitrile), 2,2xe2x80x2-azobis(2-methylbutylonitrile) and like azo compounds; iron-allene complexes; titanocene compounds; bisimidazole compounds; N-aryl glycidyl compounds; acridine compounds; combinations of aromatic ketone/aromatic amine; and peroxyketals. These photoinitiators can be used either singly or in combination.
Examples of the iron-allene complexes include those described in European Patent No. 152377. Examples of titanocene compounds include those described in Japanese Unexamined Patent Publication No. 1988-221110. Examples of peroxyketals include those described in Japanese Unexamined Patent Publication No. 1994-321895.
Of the above photoinitiators, di-t-butyldiperoxy isophthalate, 3,3xe2x80x2,4,4xe2x80x2-tetra(t-butylperoxycarbonyl)benzophenone, iron-allene complexes and titanocene compounds are preferable because of their high crosslinking or polymerizing effects.
Commercially available photoinitiators include, for example, Irgacure 651 (tradename of Ciba-Geigy for acetophenone photoradical polymerization initiator), Irgacure 184 (tradename of Ciba-Geigy for acetophenone photoradical polymerization initiator), Irgacure 1850 (tradename of Ciba-Geigy for acetophenone photoradical polymerization initiator), Irgacure 907 (tradename of Ciba-Geigy for aminoalkylphenone photoradical polymerization initiator), Irgacure 369 (tradename of Ciba-Geigy for an aminoalkylphenone photoradical polymerization initiator), Lucirin TPO (tradename of BASF for 2,4,6-trimethylbenzoyldiphenylphosphine oxide), Kayacure DETXS (tradename of Nippon Kayaku K.K.) and CGI-784 (tradename of Ciba-Geigy for titanium complex compound). These photoinitiators can be used either singly or in combination.
The photoinitiator is used in an amount of 0.1 to 25 parts by weight, preferably 0.2 to 10 parts by weight, per 100 parts by weight of the photocurable resin.
Known photosensitizing dyes are usable as photosensitizers. Examples of photosensitizing dyes include thioxanthene dyes, xanthene dyes, ketone dyes, thiopyrylium salt dyes, base styryl dyes, merocyanine dyes, 3-substituted coumarin dyes, 3,4-substituted coumarin dyes, cyanine dyes, acridine dyes, thiazine dyes, phenothiazine dyes, anthracene dyes, coronene dyes, benzanthracene dyes, perylene dyes, merocyanine dyes, ketocoumarin dyes, fumarine dyes and borate dyes. These dyes can be used either singly or in combination. Examples of borate photosensitizing dyes include those described in Japanese Unexamined Patent Publications No. 1993-241338, No. 1995-5685 and No. 1995-225474.
Also usable are unsaturated resins, which suppress the solubility of photopolymerizable compositions. For example, an unsaturated resin can be used as an agent for suppressing the solubility and like properties of a resist coating in an alkaline developer. Examples of unsaturated resins include polyester resins, alkyd resins, (meth)acrylic resins, vinyl resins, epoxy resins, phenol resins, natural resins, synthetic rubbers, silicon resins, fluororesins and polyurethane resins. These resins can be used either singly or in combination.
When a negative photosensitive resin composition is used as an organic solvent-based resin composition, the photosensitive resin composition is dissolved or dispersed in an organic solvent such as a ketone, an ester, an ether, a cellosolve, an aromatic hydrocarbon, an alcohol or a halogenated hydrocarbon.
Usable as an aqueous negative photosensitive resin composition is a known water-developable photosensitive resin composition such as an aqueous novolak phenol epoxy resin having photopolymerizable unsaturated group(s) and ion-forming group(s). Such a resin can be obtained by adding a (meth)acrylic acid to part of the epoxy groups of a novolak phenol epoxy resin to thereby introduce photopolymerizable unsaturated group(s) into the resin, followed by reaction of the epoxy groups with, for example, a tertiary amine compound to thereby form aqueous onium salt groups. The obtained resin, when exposed, is photocured and becomes insoluble in water, while unexposed portions of the resin are removable with water owing to the presence of the ion-forming group(s). Further, when the resin is post-heated (for example at about 140 to 200xc2x0 C. for 10 to 30 minutes), the ion-forming group(s) is evaporated, making the coating of the resin hydrophobic. Thus, unlike the alkali- or acid-developable photosensitive composition, the aqueous novolak phenol epoxy resin composition is capable of forming a highly resistant coating free from hydrophilic groups (such as carboxyl or amino groups) or their salts (salts formed by the developer).
Other aqueous negative photosensitive resin compositions include, for example, radical polymers obtained in a similar manner to the above, by addition reaction of a (meth)acrylic acid with a homopolymer of one of epoxy-containing radically polymerizable unsaturated monomers such as glycidyl (meth)acrylate, 3,4-epoxycyclohexylalkyl (meth)acrylate and vinyl glycidyl ether, or with a copolymer of at least one of these monomers and another radically polymerizable unsaturated monomer (such as a C1-24 alkyl or cycloalkyl (meth)acrylate, or a radically polymerizable unsaturated aromatic compound), to thereby impart photopolymerizability to the polymer, followed by reaction of the epoxy groups with, for example, a tertiary amine compound to form water-soluble onium salt groups.
The aqueous negative photosensitive resin composition, i.e., an aqueous resist composition, can be obtained by dissolving or dispersing any of the above negative photosensitive resin compositions in water.
The photosensitive resin composition can be rendered water-soluble or water-dispersible by neutralizing anionic group(s) (such as carboxyl) in the photopolymerizable composition with an alkaline neutralizing agent, or by neutralizing cationic group(s) (such as amino group(s)) in the photopolymerizable composition with an acid neutralizing agent. When the resin composition is aqueous, it can be dispersed or dissolved in water without any treatment.
The negative photosensitive resin composition is applied to the surface of the conductive coating-forming resin layer on the substrate, for example using a roller, a roll coater, a spin coater or a curtain roll coater, or by spray coating, electrostatic coating, dip coating, silk printing, spin coating or like means.
The resulting coating is set where necessary, and dried to obtain a resist coating.
A cover coat layer may be formed on the surface of the obtained resist coating before curing by exposure. The cover coat layer blocks oxygen in air and protects radicals generated by exposure from being inactivated by oxygen, so that the photosensitive material is cured smoothly by exposure.
The negative photosensitive dry film is obtained by applying a negative photosensitive resin composition to, for example, a release sheet made of polyethylene terephthalate, followed by evaporation of water or organic solvent for drying. The resulting dry film is attached to the surface of the conductive coating-forming resin layer on the substrate, and the release sheet is removed before or after irradiation with an active energy beam.
Next, the positive photosensitive resin composition will be described.
The positive photosensitive resin composition may be, for example, a resin composition containing a photo-acid generating agent, a resin and, where necessary, a photosensitizer. In the composition, the photo-acid generating agent is decomposed by light and generates an acid, which then decomposes the resin and thereby alters the polarity, molecular weight and other properties of the resin. As a result, the resin is rendered soluble in an alkaline or acid aqueous developer. The composition may contain, where necessary, another resin to adjust the solubility in the developer.
Typical examples of the positive photosensitive resin composition include a composition mainly comprising a base resin with ion-forming group(s) (e.g., an acrylic resin) which contains a quinonediazidesulfonic acid bonded via a sulfonic acid ester bond, i.e., a naphthoquinonediazide photosensitive composition in which quinonediazide group(s) is capable of being photodecomposed by light irradiation and converted to indenecarboxylic acid via ketene; and a positive photosensitive composition which shows such mechanism that the composition, when heated, forms a crosslinked coating insoluble in an alkaline or acid developer, and the crosslinked coating, when irradiated with light, becomes soluble in an alkaline or acid developer as a result of cleavage of the crosslinking structure by a function of the photo-acid generating agent which generates acid group(s) when irradiated.
The composition mainly comprising a base resin with ion-forming group(s) which contains a quinonediazidesulfonic acid bonded via a sulfonic acid ester bond may be one described in Unexamined Japanese Patent Publications No. 1986-206293 and No. 1995-133449 and other publications. The positive photosensitive composition which shows such mechanism that it forms, when heated, an insoluble crosslinked coating which, when irradiated, is rendered soluble in a developer by cleavage of the crosslinking structure, is shown in Japanese Unexamined Patent Publication No. 1994-295064, No. 1994-308733, No. 1994-313134, No. 1994-313135, No. 1994-313136 and No. 1995-146552 and other publications.
The photo-acid generating agent is a compound which generates an acid, when exposed to light. The generated acid serves as a catalyst for decomposing the resin. Known photo-acid generating agents are usable, which include, for example, sulfonium salts, ammonium salts, phosphonium salts, iodonium salts, selenium salts and like onium salts; iron-allene complexes, ruthenium-allene complexes, silanol-metal chelate complexes, triazine compounds, diazidenaphthoquinone compounds, sulfonic acid esters, sulfonic acid imide esters and halogen compounds. Also usable are photo-acid generating agents shown in Japanese Unexamined Patent Publications No. 1995-146552 and No. 1997-289218. The photo-acid generating agent can be used as mixed with or bonded to any of the above resins. The amount of the photo-acid generating agent to be used is preferably about 0.1 to 40 parts by weight, in particular about 0.2 to 20 parts by weight, per 100 parts by weight of the resin.
When the positive photosensitive resin composition is used as an organic solvent-based resin composition, the positive photosensitive resin composition is dissolved or dispersed in an organic solvent (such as a ketone, an ester, an ether, a cellosolve, an aromatic hydrocarbon, an alcohol or a halogenated hydrocarbon).
An aqueous positive photosensitive resin composition can be obtained by dissolving or dispersing the positive photosensitive resin composition in water. The positive photosensitive resin is rendered water-soluble or water-dispersible by neutralizing carboxyl group(s) or amino group(s) of the positive photosensitive resin composition with an alkaline or acid neutralizing agent.
The positive photosensitive resin composition is applied to the surface of the conductive coating-forming resin layer on the substrate, for example using a roller, a roll coater, a spin coater or a curtain roll coater, or by spray coating, electrostatic coating, dip coating, silk printing, spin coating or like means.
The organic solvent-based or aqueous positive photosensitive resin composition applied on the substrate is set where necessary, and dried at about 50 to 130xc2x0 C. to obtain a positive photosensitive coating.
The positive photosensitive dry film can be obtained by applying the positive photosensitive resin composition to, for example, a release sheet made of polyethylene terephthalate, followed by evaporation of water or organic solvent for drying, or heating for curing. The release sheet is removed after attaching the resulting dry film to the surface of the conductive coating-forming resin layer on the substrate.
The organic solvent-based negative heat-sensitive resin composition for forming the energy beam-sensitive coating layer is a solution or dispersion in an organic solvent, of a resin composition crosslinkable with heat rays such as infrared rays. The resin composition may be a known resin composition, such as hydroxyl-containing resin/amino resin; hydroxyl-containing resin/blocked isocyanate; hydroxyl-containing resin/melamine resin; hydroxyl-containing resin/silicon resin containing hydrolyzable group(s) such as alkoxysilyl or hydroxysilyl; hydroxyl-containing resin/hydrolyzable group-containing acrylic resin; epoxy resin/phenol resin; epoxy resin/carboxylic acid or carboxylic anhydride; epoxy resin/polyamine; unsaturated resin/radical polymerization catalyst (such as peroxide); or an olefinic unsaturated compound containing ether bond(s) and carboxyl and/or hydroxyphenyl.
The aqueous negative heat-sensitive resin composition may be one prepared as follows: acid or basic group(s) is incorporated into a resin comprised in any of the above resin compositions crosslinkable by heat rays such as infrared rays, and the resin is then neutralized with a basic compound or acid compound and dissolved or dispersed in water.
The negative heat-sensitive dry film can be obtained by applying a negative heat-sensitive resin composition to, for example, a release sheet made of polyethylene terephthalate, followed by evaporation of water or organic solvent for drying. The dry film is attached to the surface of the conductive coating-forming resin layer on the substrate, and the release sheet is removed before or after irradiation with an active energy beam.
The combination of the energy beam-sensitive coating layer/conductive coating-forming resin layer for use in the step (1) may be, for example, photocurable energy beam-sensitive coating layer/photocurable conductive coating-forming resin layer; photocurable energy beam-sensitive coating layer/heat-curable conductive coating-forming resin layer; heat-curable energy beam-sensitive coating layer/photocurable conductive coating-forming resin layer; heat-curable energy beam-sensitive coating layer/heat-curable conductive coating-forming resin layer; photocurable energy beam-sensitive coating layer/non-curable conductive coating-forming resin layer; or heat-curable energy beam-sensitive coating layer/non-curable conductive coating-forming resin layer. As described above, the curablility of the conductive coating-forming resin is such that the resin layer is not substantially cured by the energy beam irradiation of the energy beam-sensitive coating layer, but is cured (post-cured) by post-treatment with heat, light or the like carried out after development of the energy-beam sensitive coating layer.
The energy beam-sensitive coating layer may be of negative type or positive type. Also, the conductive coating-forming resin layer may be of negative type or positive type.
In the case where the energy beam radiated onto the surface of the energy beam-sensitive coating layer is heat rays, a conductive coating-forming resin layer is usable which has no heat-sensitivity or less heat-sensitivity than the energy beam-sensitive layer, and which is substantially non-curable by irradiation with the heat rays.
For curing the energy beam-sensitive coating layer alone by irradiation with heat rays without curing the conductive coating-forming resin layer, conditions such as type of heat rays, irradiation time and amount of irradiation energy are suitably selected so that the energy beam-sensitive coating layer receives sufficient heat to facilitate development while the conductive coating-forming resin layer is prevented from adverse effects of the development. The resin compositions in the energy beam-sensitive coating layer and the conductive coating-forming resin layer may be the same, but preferably they are different from each other to achieve improved results. The combination of heat-curable layers of different types is, for example, heat-sensitive energy beam-sensitive coating layer/heat-curable conductive coating-forming resin layer, such as blocked polyisocyanate curable resin layer/an amino curable resin layer.
In the case where the energy beam radiated onto the surface of the energy beam-sensitive coating layer is a light beam, a conductive coating-forming resin layer is usable which has no photosensitivity or less photosensitivity than the energy beam-sensitive layer, and which is substantially non-curable by irradiation with the light beam. For curing the energy beam-sensitive coating layer alone by irradiation with a light beam without curing the conductive coating-forming resin layer, conditions such as type of light beam, irradiation time and amount of irradiation energy are suitably selected so that the energy beam-sensitive coating layer receives sufficient light to facilitate development while the conductive coating-forming resin layer is protected from adverse effects of the development. The resin compositions of the energy beam-sensitive coating layer and the conductive coating-forming resin layer may be the same, but preferably they are different from each other to achieve improved results. The combination of photocurable layers of different types is, for example, photosensitive energy beam-sensitive coating layer/photosensitive conductive coating-forming resin layer; or visible light-sensitive resin layer/ultraviolet light-sensitive conductive coating-forming resin layer.
Further, the conductive coating-forming resin layer may be a heat-curable conductive resin layer when the energy beam radiated onto the surface of the energy beam-sensitive coating layer is a light beam, and may be a photocurable conductive resin layer when the energy beam is heat rays.
In the above manner, the step (1) forms a conductive coating-forming resin layer and an energy beam-sensitive coating layer deposited on a substrate in this order.
Step (2)
In the step (2), the surface of the energy beam-sensitive coating layer deposited on the conductive coating-forming resin layer on the substrate is irradiated with an active energy beam or heat rays, directly or through a mask, so as to obtain a desired pattern.
The negative photosensitive resin coating obtained by applying an organic solvent-based or aqueous negative photosensitive resin composition to the surface of the conductive coating-forming resin layer on the substrate is irradiated with a light beam for photocuring, so as to obtain a desired resist coating (image).
The positive photosensitive resin coating obtained by applying an organic solvent-based or aqueous positive photosensitive resin composition to the surface of the conductive coating-forming resin layer on the substrate is irradiated with a light beam to decompose the resin, so as to obtain a desired resist coating (image).
Light sources usable for photocuring or photodecomposition are not limited and include, for example, an extra-high pressure, high-pressure, medium-pressure or low-pressure mercury lamps, chemical lamps, carbon arc lamps, xenon lamps, metal halide lamps and tungsten lamps. Also usable are various lasers that produce an oscillating beam in the visible region, such as argon lasers (488 nm), YAG-SHG lasers (532 nm) and UV lasers (351 to 364 nm).
The negative heat-sensitive resin coating obtained by applying an organic solvent-based or aqueous negative heat-sensitive resin composition to the surface of the conductive coating-forming resin layer on the substrate is irradiated with heat rays for curing, so as to obtain a desired resist coating (image).
Usable heat rays include, for example, semiconductor laser beams (830 nm) and YAG laser beams (1.06 xcexcm).
In this manner, the step (2) performs energy beam irradiation of the surface of the energy beam-sensitive coating layer deposited on the conductive coating-forming resin layer on the substrate, so as to obtain a desired pattern.
Steps (3), (4) and (3xe2x80x2)
After irradiation of the energy beam-sensitive coating layer with an energy beam in the step (2), the steps (3) and (4) or the step (3xe2x80x2) are carried out to form a conductive pattern by developing the energy beam-sensitive coating layer and the conductive coating-forming resin layer sequentially or simultaneously.
When the energy beam-sensitive coating layer is formed from a negative photosensitive resin composition or a negative heat-sensitive resin composition, unexposed portions (portions not irradiated with a light beam or heat rays in the step (2) to obtain a desired resist coating (image)) of the coating layer are removed by development using a developer.
When the energy beam-sensitive coating layer is formed from a positive photosensitive resin composition, exposed portions (portions irradiated with a light beam in the step (2) to obtain a desired resist coating (image)) of the coating layer are removed by development using a developer.
When the positive photosensitive resin composition is an anionic composition, alkali development is performed, and when the positive photosensitive resin composition is a cationic composition, acid development is carried out. Alternatively, water development can be carried out when the positive photosensitive resin composition comprises a water-soluble resin mentioned above (such as onium salt group-containing resin). The developer for such treatment may be any of those employed for removal of the conductive coating-forming resin layer, which will be mentioned hereinafter.
The revealed portions of the conductive coating-forming resin layer is removed by chemical means such as liquid developer treatment, or by physical means such as sandblasting.
In the liquid developer treatment, the energy beam-sensitive coating layer and the conductive coating-forming resin layer can be developed sequentially in this order or simultaneously. Conditions for development are not limited, but are preferably as follows: For sequential development, the energy beam-sensitive coating layer is developed at a developer temperature of about 10 to 50xc2x0 C., preferably about 15 to 40xc2x0 C., for a developing time of about 10 seconds to 20 minutes, preferably about 15 seconds to 15 minutes, and the conductive coating-forming resin layer is developed by immersion in a developer at a temperature of about 10 to 80xc2x0 C., preferably 15 to 50xc2x0 C., for a developing time of about 15 seconds to 60 minutes, preferably 1 minute to 20 minutes. For simultaneous development, the overlapping range of the above conditions is preferably employed.
The liquid development of the energy beam-sensitive coating layer and conductive coating-forming resin layer is carried out using an alkaline developer in the case where acid group(s) is contained in the resin for forming the energy beam-sensitive coating layer or the conductive coating-forming resin layer. When basic group(s) is contained in the resin, an acid developer can be used. When hydrophilic group(s) is contained in the resin, water can be used as a developer. When the resin is soluble or dispersible in an organic solvent, an organic solvent can be used as a developer.
Examples of alkaline developers include aqueous solutions of monomethylamine, dimethylamine, trimethylamine, monoethylamine, diethylamine, triethylamine, monoisopropylamine, diisopropylamine, triisopropylamine, monobutylamine, dibutylamine, monoethanolamine, diethanolamine, triethanolamine, dimethylaminoethanol, diethylaminoethanol, ammonia, caustic soda, caustic potash, sodium metasilicate, potassium metasilicate, sodium carbonate, tetraethylammonium hydroxide and the like.
Examples of acid developers include aqueous solutions of formic acid, crotonic acid, acetic acid, propionic acid, lactic acid, hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid and the like.
It is preferable that the concentration of the acid or alkaline substance in the developer is usually about 0.05 to 10 wt. %.
Usable organic solvents include, for example, hexane, heptane, octane, toluene, xylene, dichloromethane, chloroform, carbon tetrachloride, trichloroethylene and like hydrocarbon solvents; methanol, ethanol, propanol, butanol and like alcohol solvents; diethyl ether, dipropyl ether, dibutyl ether, ethyl vinyl ether, dioxane, propylene oxide, tetrahydrofuran, cellosolve, methyl cellosolve, butyl cellosolve, methyl carbitol, diethylene glycol monoethyl ether and like ether solvents; acetone, methyl ethyl ketone, methyl isobutyl ketone, isophorone, cyclohexanone and like ketone solvents; methyl acetate, ethyl acetate, propyl acetate, butyl acetate and like ester solvents; and pyridine, formamide, N,N-dimethylformamide and other solvents.
The method of sandblasting can be suitably selected according to the material and thickness of the resin layer. For example, calcium carbonate particles, glass beads or like particles having a diameter of 10 to 30 xcexcm are blasted at a pressure of about 1 to 3 kg/cm2, to form a conductive pattern. The temperature of the atmosphere for development by this method is not limited, and may be usually about 10 to 100xc2x0 C., preferably about 20 to 80xc2x0 C.
In the above manner, the steps (3) and (4) or (3xe2x80x2) form a desired conductive pattern.
Conductive patterns formed by the method of the present invention include, for example, conductive patterns for black matrixes, conductive patterns for color filters, conductive patterns for various display panels, and conductive patterns for plastic substrates or buildup plastic substrates.
In the method of the invention, where necessary, the energy beam-sensitive coating layer remaining on the pattern formed by development of the conductive coating-forming resin layer can be decomposed by irradiation with an active energy beam and removed by dissolution in a developer.
Also, the pattern of the conductive coating-forming resin layer formed in the step (4) or (3xe2x80x2) can be, where necessary, crosslinked and post-cured by heating or irradiation with an active energy beam.
After the step (3xe2x80x2) or (4), the energy beam-sensitive coating layer can be removed from the pattern by a known method. For example, an energy beam-sensitive coating layer containing acid group(s) can be removed using an aqueous alkali solution; an energy beam-sensitive coating layer containing basic group(s) can be removed using an aqueous acid solution; and an energy beam-sensitive coating layer soluble in an organic solvent can be removed using an organic solvent.
Also, after development of the conductive coating-forming resin layer (formation of a pattern), the pattern may be crosslinked or baked, by heating, allowing to stand at room temperature or exposure to light.
The method of the invention is applicable for any purposes without limitation, as long as the method comprises the above steps.
The conductive pattern formed by the method of the invention can be used, where necessary, in combination with an insulating coating or an insulating pattern coating.
Typical embodiments of the present invention are briefly described below. It should be noted, however, the present invention is not limited to these embodiments.
(I) Method of Forming Transparent Electrodes for Display Panels
A transparent conductive coating layer (a conductive coating-forming resin layer according to the invention) is formed on the whole of one surface of a glass substrate, and an energy beam-sensitive coating layer is deposited on the surface of the resulting transparent conductive coating layer. Subsequently, the surface of the energy beam-sensitive coating layer is irradiated with an active energy beam directly or through a pattern mask so as to obtain a desired pattern on the transparent conductive coating layer. The energy beam-sensitive coating layer is developed, and the revealed portions of the conductive coating-forming resin layer are developed, and then the energy beam-sensitive coating layer is removed from the pattern, thereby giving a transparent electrode pattern. Alternatively, the energy beam-sensitive coating layer and the conductive coating-forming resin layer may be simultaneously developed. The resin for forming the transparent conductive coating layer preferably has a glass transition temperature higher than the temperature employed for development of the conductive coating layer.
After developing, the transparent conductive coating layer is baked, for example, at about 300xc2x0 C. to 800xc2x0 C. for about 20 to 60 minutes to thereby form a conductive pattern coating.
By the baking step, the conductive coating-forming resin component is evaporated, and the remaining transparent conductive pigment component undergoes fusing, melting or the like so as to form a transparent conductive coating.
The energy beam-sensitive coating layer can be removed by the baking step.
Examples of transparent conductive pigments include ITO and tin dioxide.
(II) Method of Forming Colored Electrodes for Display Panels
A colored conductive coating layer (a conductive coating-forming resin layer according to the invention) is formed on the whole of one surface of a glass substrate, and an energy beam-sensitive coating layer is deposited on the surface of the resulting colored conductive coating layer. Subsequently, the surface of the energy beam-sensitive coating layer is irradiated with an active energy beam directly or through a pattern mask so as to obtain a desired pattern on the colored conductive coating. The energy beam-sensitive coating layer is developed, and revealed portions of the colored conductive coating-forming resin layer are developed, and then the energy beam-sensitive coating layer is removed from the pattern, thereby giving a colored electrode pattern. Alternatively, the energy beam-sensitive coating layer and the conductive coating-forming resin layer can be simultaneously developed. The resin for forming the colored conductive coating layer preferably has a glass transition temperature higher than the temperature employed for development of the conductive coating layer.
After development, the colored conductive coating layer is baked, for example, at about 300xc2x0 C. to 800xc2x0 C. for about 20 to 60 minutes to thereby form a conductive pattern coating.
By the baking step, the conductive coating-forming resin component is evaporated, and the remaining color conductive pigment component undergoes fusing, melting or the like so as to form a colored conductive pattern coating.
The energy beam-sensitive coating layer can be removed by the baking step.
Examples of color conductive pigments usually used include silver, copper and nickel. These pigments can be used, where necessary, in combination with a color pigment such as carbon black.
These methods of the invention can be combined to form, for example, patterns for bus electrodes or address electrodes for plasma displays, which comprises a transparent electrode pattern layer and a black or silver conductive coating layer deposited on the whole or part of the transparent electrode pattern layer.